This invention relates to a method and apparatus for detecting a particulate substance in a liquid and more particularly to a detection method and apparatus of an immunoreaction product which may be suitable for detecting a trace amount of an immunoreaction product.
Conventional methods and apparatuses for detecting very small particles in a liquid in accordance with photoacoustic spectroscopy are not equipped with a control mechanism which controls the wavelength of excitation light in such a manner as to bring it into conformity with the size of the very small particules as the object of measurement, as can be seen, for example, from Japanese Patent Laid-Open No. 102541/1986. They do not either consider any mechanism which detects selectively particulate substaces having a specific size dependence of sensitivity of an photoacoustic spectrometry and determines the quantity of the particulate substances. Therefore, the prior art technique does not consider selective detection and determination of a reaction product such as an immunoreaction product in the system where an antibody, antibody support particles and reaction products coexist during non-reaction.
The prior art technique described above does not take into consideration the particle size dependency of sensitivity of the photoacoustic spectrometry and cannot selectively detect and determine very small particles having specific sizes such a rheumatuid factors, cancer specific antigens, and the like.